To recap, in the field when you need a photo above ISO 800, set the camera to an ISO at least 1 and perhaps 2 stops lower than what you think is indicated. Viewfinder will still be usable, and you can fix the ISO in raw post-processing.

Make sure you try this idea before you buy it. A few years ago I did that experiment and found that it was possible to "fix" such a shot using esoteric software and elaborate methods, and while the noise was equivalent the colour in the shadows was never quite as good as the shot with the ISO that gave normal/desirable image brightness. In my case there was no pay-off to justify doing more work to get an inferior result.